The Unknown Terror

Six months after the disappearance of spelunker Jim Wheatly in South America, Wheatly's brother-in-law, Dan Mathews, decides to return to South America and find him. Wheatly vanished while searching for the Cave of the Dead, and so Dan hires Raul Kom, an Indian who lives in the region of the mythical cave, to lead him there. Gina, Dan's wife, is eager to join the search for her brother, but Dan needs an experienced spelunker to accompany them. Pete Morgan, who suffered a serious accident that rendered him partially crippled while exploring a cave with Dan, asks to join the expedition, and Dan, feeling responsible for Pete's condition, welcomes him even though Pete was once Gina's lover. Once they reach Raul's village, the Indians become agitated upon spotting the expedition's gear and soon after, Raul disappears. Upon discovering that Ramsey, an American doctor, is living in the village, the party go to introduce themselves and find Ramsey canning a batch of fruit. The doctor, who has resided in the area for fifteen years, explains that he is doing research on native plants and has discovered a remarkable, rapid-growing fungus. When Dan questions him about the cave, Ramsey becomes sinister and refutes its existence. At dinner, the sounds of drums beat ominously in the distance, and when Ramsey's Indian wife, Concha, breaks one of the jars of fruit, a mold-like fungus oozes from the bottle. As a storm brews that night, Dan and Gina go to the village in search of Raul, and when they offer one of the villagers money to lead them to him, he shows them Raul's tongue, which has been ripped from his mouth. Later, Concha takes Pete and Dan to a secluded spot to hear what she calls "voices of the souls in purgatory." Alone in the house, Gina is terrified when an unearthly creature comes to the window. Panicked, Gina runs screaming into the jungle, where she is encircled by more of the creatures. Gina cowers and covers her eyes in fear, and when she looks up, the creatures have vanished. Drawn by her screams, Dan finds Gina and takes her home. Later that evening, Lino, one of the villagers, comes to the house and after showing them Wheatly's knife, offers to guide them to the cave. Pete, Lino and Dan ride horseback to the underground cave, and Lino waits outside as Pete and Dan penetrate its mouth. At the bottom, 200 feet down, they find Raul's dead body, a roiling pool of water and Wheatly's shovel at the opening of a tunnel that has been sealed by a rockslide. As a storm rages outside, Dan and Pete uncover the opening and Dan insists on entering the tunnel first. Just then, the tunnel is flooded by onrushing water and Pete scurries to higher ground and rushes to the doctor's house to report that Dan is trapped. Thinking that the only way to rescue Dan is to swim into the tunnel, Pete packs his diving gear and Ramsey offers Lino's service to carry the equipment pack. Gina accompanies them, but when they reach the cave, the water has receded, allowing them to dig out the opening. Pete climbs in first, and after Gina follows, Lino pulls a bomb from the pack and tosses it after her, sealing the cave. Gina and Pete find Dan lying on the floor, his back broken. Soon after, a group of creatures covered with fungus emerges from the cave's crevices, and Pete realizes that Ramsey has been conducting his fungus experiments on people. Observing fungus oozing through the tunnels, Pete deduces that the passageway must lead to Ramsey's house. Leaving Gina to stay with Dan, Pete makes his way to the doctor's back door and breaks it in. Asserting that nothing can kill the fungus, Ramsey states that they must blow up the cave before the fungus can take over. After instructing Concha to pull the switch that is wired to explosives set to detonate the cave, Ramsey and Pete return to rescue Dan and Gina. Ramsey is killed in the ensuing explosion, and just as Pete reaches Gina, Dan dies. Hoping that the pool leads to the ocean, Pete and Gina don their diving gear, plunge in the water and swim through the tunnel to reach a safe, secluded cove.